With increasing development of high technology industries, computers become essential electronic apparatuses in our daily lives. For example, computers are employed for work or amusement purposes. For a purpose of performing specialized functions, a computer system may also include one or more peripheral devices linked to the host computer. Examples of the peripheral devices include speakers, printers, monitors, scanners or other electronic load products. Usually, the power cords of the host computer and the various peripheral devices are plugged in a multi-outlet power strip device. Since multiple electronic load products are simultaneously plugged in the power outlets of the power strip device, overloading will be a safety problem with the multi-outlet power strip device.
Referring to FIG. 1, a schematic perspective view of a conventional power strip device is illustrated. The power strip device 1 has a manual power switch 10 for selectively enabling or disenabling the multiple power outlets to receive power or prevent electrical current from being delivered.
For complying with safety regulations of operating computers, when the computer is powered off, the user needs to manually switch the manual power switch 10 into an open state to interrupt the flow of the utility power source to the power strip device 1. Since the flow of the utility power source to the power strip device 1 is interrupted, the hazards resulting from sparking of electric wires are reduced and power consumption is avoided. On the other hand, if the computer users forget to switch the manual power switch 10 into the open state, many load products are still running to consume power and thus the life of these load products may be shortened. For solving these problems, some power strip devices have been developed to automatically cut off the electricity to the power outlets while powering off the host computer.
For example, such a power strip device is disclosed in Taiwanese Patent No. M304817, and the contents of which are hereby incorporated by reference. Referring to FIG. 2, a schematic circuit diagram of the power strip device disclosed in Taiwanese Patent No. M304817 is illustrated. The power strip device 2 of FIG. 2 principally includes a master power outlet 21, a slave power outlet 22, a serial control bus 23, a control circuit 24, an electrical switch 25, a surge protector 26 and an indicator light circuit 27. An example of the serial control bus 23 is a universal serial bus (USB), which includes two power lines (VCC, GND) and two data lines (D+, D−). Hereinafter, the operation principle of the power strip device will be illustrated as follows. When the serial control bus 23 is electrically connected to the computer (not shown), a data signal DS is transmitted to control chip U1 of the control circuit 24 through the data line D+. In response to the data signal DS, a control signal CS is outputted through the output terminal of the control chip U1 to control the changeover switch Q1. In response to the control signal CS, the changeover switch Q1 is switched to an ON state or an OFF state. In a case that the changeover switch Q1 is in the ON state, driving power is transmitted to the electrical switch 25 through the power line VCC of the serial control bus 23 and the control circuit 24, and thus the electromagnetic coil MS of the electrical switch 25 is magnetized. The magnetized electromagnetic coil MS allow the changeover point OC to switch to the ON position. Meanwhile, the utility power source may be conducted to the slave power outlet 22 through the surge protector 26, thereby enabling the slave power outlet 22 and allowing an electronic load product (not shown) to be plugged therein.
On the contrary, in a case that the changeover switch Q1 is in the OFF state, the control circuit 24 interrupt the flow of the driving power VCC to the electromagnetic coil MS of the electrical switch 25 to demagnetize the electromagnetic coil MS. The demagnetized electromagnetic coil MS allow the changeover point OC to switch to the OFF position. Meanwhile, the utility power source is shut off and no longer conducted to the slave power outlet 22 through the surge protector 26, thereby disenabling the slave power outlet 22 and preventing electrical current from being delivered to the electronic load product (not shown).
As previously described, the power strip device 2 has a function of automatically cutting off the electricity to the power outlets while powering off the host computer. That is, when the host computer is powered off and no electrical current is conducted through the master power outlet 21, the slave power outlet 22 is disenabled. As a consequence, the benefits of safety and power-saving are both achieved. Unfortunately, this power strip device 2 still has some drawbacks. For example, since the driving power VCC is necessary to magnetize the electromagnetic coil MS of the electrical switch 25, another power-saving problem occurs. That is, additional consumption of the driving power VCC compromises the power-saving effect of the power strip device 2.
Therefore, there is a need of providing an improved power strip device having an enhanced power-saving effect.